1. Technical Field
The invention is related to improving the appearance of digitized or digital images, and more particularly to a system and process for improving the appearance of improperly exposed and/or improperly colored images.
2. Background Art
Color images captured with a digital camera or obtained by scanning (i.e., digitizing) photographs can exhibit a less than appealing appearance owing to under or over exposed pixels and improperly colored pixels. In the case of exposure, capturing an image or taking a photograph using the proper exposure is often a difficult task. Several factors can contribute to poorly exposed images and photographs. For example, modern cameras often have automatic systems for estimating the proper exposure. However, these systems are sometimes fooled owing to the lighting conditions or atypical characteristics of the scene being captured. In addition, these modern cameras, as well as their predecessors, often allow the photographer to manually adjust the exposure setting, thereby introducing the possibility of human error.
Improperly colored pixels typically occur because the colors of images recorded by a camera depend on the spectral characteristics of the camera optics, the lighting conditions of the scene and the characteristics of the color filters employed in the camera. As a result, the primary color data captured may not be a faithful rendition of the actual colors found in the scene.
To resolve the problems of improperly exposed and colored images, post-capture corrective measures are often employed. There are two categories of systems. In the first category, the systems that implement these corrective measures can be manual in that, for example, a user views the image on a computer screen and employs a user interface to interactively adjust the color and/or exposure. In the second category, the systems provide for automatic correction of color and/or exposure in an image. In these systems, a user typically just accesses the image, which can be viewed on a computer screen, and activates an automatic correction program. This activation can be implicit, in the sense that the automatic correction program is called whenever the image is accessed; it can also be explicit, in which case the user clicks on a button to call the correction program when necessary. The present invention falls into this latter automatic correction category.